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Tetramethylammonium fluoride

Tetramethyl­ammonium fluoride is the quaternary ammonium salt with the formula (CH3)4NF. This hygroscopic white solid is a source of “naked fluoride": fluoride ions not complexed with a metal atom. Most other soluble salts of fluoride are in fact bifluorides, HF2–. Historically, there have been two main approaches to prepare tetramethyl­ammonium fluoride: hydrofluoric acid neutralization of tetramethyl­ammonium hydroxide, and salt metathesis between different ammonium salts and inorganic fluoride sources, such as KF or CsF.[1] Because the fluoride anion is extremely basic, the salt slowly reacts with acetonitrile, inducing dimerization to CH3C(NH2)=CHCN, which co-crystallizes.[2]

Related salts

(CH3)3P=CH2 + KHF2 → (CH3)4PF + KF
Gaseous tetramethylphosphonium fluoride exists as the phosphorane but autoionizes in acetonitrile solution.[3] A more elaborate phosphazenium salt ([(CH3)2N)3P]2N+F−) is also known.[4]

References

  1. ^ Iashin, Vladimir; Wirtanen, Tom; Perea-Buceta, Jesus E. (2022-02-18). "Tetramethylammonium Fluoride: Fundamental Properties and Applications in C-F Bond-Forming Reactions and as a Base". Catalysts. 12 (2): 233. doi:10.3390/catal12020233. hdl:10138/340938. ISSN 2073-4344.
  2. ^ Christe, K. O.; Wilson, W. W.; Wilson, R. D.; Bau, R.; Feng, J. A. (1990). "Syntheses, Properties, and Structures of Anhydrous Tetramethylammonium Fluoride and Its 1:1 Adduct with trans-3-Amino-2-butenenitrile". Journal of the American Chemical Society. 112 (21): 7619–7625. doi:10.1021/ja00177a025.
  3. ^ Kornath, Andreas; Neumann, F.; Oberhammer, H. (2003). "Tetramethylphosphonium Fluoride: "Naked" Fluoride and Phosphorane". Inorganic Chemistry. 42 (9): 2894–2901. doi:10.1021/ic020663c. PMID 12716181.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ Schwesinger, Reinhard (2001). "1,1,1,3,3,3-Hexakis(dimethylamino)-1λ5,3λ5-diphosphazenium Fluoride". e-EROS Encyclopedia of Reagents for Organic Synthesis. pp. 1–2. doi:10.1002/047084289X.rh014m. ISBN 0471936235.
  5. ^ Haoran Sun & Stephen G. DiMagno (2005). "Anhydrous Tetrabutylammonium Fluoride". Journal of the American Chemical Society. 127 (7): 2050–1. doi:10.1021/ja0440497. PMID 15713075.